Solvent extraction of asphaltic residues



Sept l, 1953 R. c. wol-:RNER 2,650,897

SOLVENT EXTRACTION OF ASPHALTIC RESIDUES Filed May 2l, 1949 2 Sheets-Sheet l ATTORNEYS Sept l 1953 R. c. woERNER 2,650,897

SOLVENT EXTRACTION OF ASPHALTIC REISIDUES Filed May 21. 1949 2 sheets-sheet 2 OzZ f Ear/ane f4? 'l Ez'zmcz'an INVENTOR. )yada/h C//efmvr ATTORNEYS Patented Sept. 1, 1953 SOINENT EXTRACTI RE SID N OF ASPHALTIC UES Rudolph C. Woerner, Homewood, .designer ,to

Sinclair Reflnn a corporation of Company, New York, N. Y., aine Application May 21. 1949, Serial No. i583 1 Claim. l

Application Serial No.'94,'708, of D. V. Fitz and J. Martin, iiled May 21, 1949, and now abansdoned, discloses a method of recovering useful l,oily:compositions in sizable yields from petroleum Ecouzehalts by butane extraction. -One of the criti- .cal Afactors in treating Aasphalt with a butane is .securing an eiiective degree of contact and my .invention `relates to an improved method for obeifective asphalt-butano contact Vin a continuous contacting system which results in improved :product quality and yield.

The effective contacting of butane solvent and asphalt is of practical significance since it is in great part determinative of the quality and yield of the extracted oil. Yield and quality are, of course, in the last analysis indicative of the commercial practicability of any such process, but in the treatment of asphalt with butano, yield and quality are in a sense mutually opposed. Thus yield increases with solubility, but in general, Quality improves with sharpness of separation between the heavy oily constituents and the tarry or asphaltic constituents.

One of the diillculties in treating solid asphalt .-with a `butane for oil recovery is that solubility decreases with increasing temperature. 'I'his Vcomplicates contacting eficiency. for under the .operating 4temperatures required for commercially .attractive yields the asphalt feedis very viscous. Direct Y contacting i of feed .and raw solvent tends to lump Yup the fasphala: causing f apparatus ,plugsging ,dimculties and resulting inipoor recoveries. zMcreover, I have found thatit is diicult ,to mix Vlin increments of solvent with the feed so asyto increase Vfluidity `beinre entering the extraction zone. Solubility is still too low at temperatures above the asphalt melting point. Since asphalt is plastic in character and not susceptible to pulverization, the intimate contact necessary for ecient extraction demands some liquid to liquid i contact, and of course it is also desirable to handle the asphalt as a liquid for convenience and to hold down solvent requirements. I have discovered, however, that if contact between raw solvent and asphalt feed is minimized, andthe feed `is rst contacted with an oily butane, for example, a circulating slurry stream from the extraction zone, handling and circulating diliiculties are greatly reduced while both yield and product quality arev significantly improved.

The'extraetionmay be accomplished in onefor more contacting stages with separationof an oil fraction in Vfat solvent and a spent asphalt fraction, followed by appropriate steps =for solvent recovery and recycle, and stabilization ofprod- (Cl. 12S-14.46)

2 uct. Enr tniaxnple, in single-stage contacting. the asphalt feed may be initially mixed with an foily butano, e. g.. a circulating slurry of fiat solvent and asphalt, before introduction to the extraction -aone where it contacts the main solvent stream. In a two-stage system, Vfor Iexample. the freshasphaltmay be preliminarilymi-xed with an foily butane and then charged to a separating .zone A stream of partially spent 1asphalt is then admixed with -f-resh butane and charged to a second vseparating zone, from which the Adeoiled .asphalt `is recovered.

In the process the `nature of the solvent is important; however, either n-butane or iSObuvtane gives Yuseful recoveries of good quality oils. The temperature must be below `the critical temperature of the'sclvent `and a pressuresuicient to maintain the solvent in the liquid phase is employed. :Yield may be controlled conveniently through regulation of the top extraction tempervxnture. It-has been found that solvent to feed raticsabove about 5 to 1 are necessary for useful yield, and solvent ratios above about Vlll 'to 1 are `usually.highly ydesirable from the standpoint of `yield and product quality. The relationship of solvent vratio andtemperature. however, gives a degree Vof latitude in that lower solvent ratios may he partially lcompensated for by reducing temperature. With n-butane. Vyields of upwards -of 40 volume per cent of oil maybe obtained with -aitopmxtrectiontemperature of, say. about 280 F. at vabout 1'500 p. s. i. Thelsolubiitycf isobu- Etane s more limited, and yields of upwards of about 20 volume per cent fare obtained at a tcp-extraction temperature of,-say, about 250 F. and apressure of :about 420 p. s. i.

My linvention will be illustrated in Figures 1 and 2 `ofthe accompanying drawings whichrepresent the flow somewhat diagrammatically. Figure 1 is ,illustrative of a two-stage process embodying my invention; Figure 2,s illustrative of thedmrentio,ny adapted toa c ountercurrent con- V tactin a column.

VElgurel illustrates an essentially continuous contacting process for commercial extraction of heavy oils from asphalt with a butane solvent.

Fresh-asphalt is introduced through line I 0 and contacted with oily" butane from lines l land l2. The contact mixture is preferably thoroughly agitatedlinsmixing zone I3. The mixturey is then -passedlbyfline M tothe rst stage settling zone fk5, .above which is situated stripping .section t6 ladvantageously containingV `a series. of` steam -coils l1, heated by steam introduced through line iB. The coils II maintainadifferential temperature 3 between the top and bottom of the stripping column, thereby improving product quality and yield. The mixture of asphalt and oily butane is introduced above the asphalt-butane level I9 in the first settling zone. The oil-butane product is taken oif through line 30 and is passed to a debutanizer (not shown). Oily butane is taken from the first settling zone by means of line 2|) and is recirculated by contact with the fresh asphalt feed. Partially spent asphalt, containl ing butane, is taken from the bottom of the settling zone by line 2| and contacted with fresh butane entering through line 22. Part of this mixture may be recirculated as desired in the first settling zone by means of line 23. The fresh butane-partially spent asphalt mixture from line 2| is further contacted with another partially spent asphalt-butane slurry from the line 24, all are thoroughly mixed in mixing zone and then passed into the second settling zone 26 by line 2l, above the asphalt-butane level I9. Spent asphalt, containing butane, is taken from the second settling zone 26 by means of well 23 and line 29, from which it may be passed to a stabilizer (not shown) Oily butane is taken from this settling zone by line 30 and recirculated to the first settling zone, although a portion of the mixture may be contacted with the fresh butanespent asphalt mixture by means of line 3l.

The asphalt-butane levels i9 in the settling zones may be regulated by liquid level control valves, comprising a floating bulb 32 which releases valve 33 at the desired level. The process as described may also include pumps and valves as illustrated so as to accurately regulate the various flow streams and treatment zones.

Figure 2 illustrates a column contacting process embodying my invention.

Fresh butane, introduced through line 40, is contacted with a spent asphalt-butane mixture 42 taken from below the tar level in extraction zone 45 by line 4|. This mixture is thoroughly agitated in mixing zone 43, most advantageously by use of mechanical stirrer 44, and passed to extraction zone 45 by line 46. An oil-butane product is taken off by line 41 and a spent asphaltbutane product by line 48. The oil-butane mixture is passed to a debutanizer (not shown), While the spent asphalt-butane product is passed to a butane stripper (also not shown). The extraction zone 45 is preferably an extraction column containing steam coils 49 in its upper portion so as to create a differential temperature betwen top and bottom, thereby resulting in improved quality and yield. Fresh asphalt feed is introduced through line 50, and contacted with a recycle slurry of oily butane from line 52. These components are thoroughly mixed in mixing zone 53, preferably by use of mechanical stirrer 54, and then are passed into the extraction zone 45 by line 56.

The spent asphalt-butane level 5l in the extraction zone 45 may be regulated by a liquid level control valve comprising a floating bulb 54 which releases valve 55 at the desired level. Suitably located pumps and valves may be used as illustrated.

The effect of contact efciency on yield and product quality, together with the principles of my invention, will be illustrated in the following examples. In these examples the carbon residue, taken according to the Conradson method, is indicative of product quality as it tends to x the other properties, including tackiness. High 4 viscosities are desired, together with a reasonably low optical density color.

The tests on the asphalt feed utilized are set forth below:

Specific gravity at 77 F./77 F 1.052

Sft. pt 156 Carbon residue, weight percent 27 Penetration at 77 F 4 EmampleI Extraction from asphalt with normal butane was first attempted by countercurrent contacting in a 4-inch by 15-foot extraction tower equipped with a top internal heater for the purpose of maintaining a differential temperature. The tower was packed with Raschig rings to improve contact, but upon contact of feed and solvent, the packing plugged solid with asphalt so that flow could not be continued.

Example II A light stream of isobutane was mixed with asphalt feed in a commingler and the resulting mixture injected into about the middle of the column from which the Raschig rings had been removed. A main stream of isobutane was introduced into the column so as to contact the streams countercurrently. An isobutane-oil overhead was taken olf, while the deoiled asphalt containing isobutane, was a bottoms product. The solvent-feed ratio was 14 to l. A summary of the pertinent data for this run follows:

C. rbon Residue, Wt. Percent.

" l Vol. Percent.

Gravity,o A.T.l 12.5 13.5 Sit. Pt. ol Silent Asphalt, F 190 185 lxtr. Col. Top Temp., F 250 265 Although the process was operable, the contacting was not highly eicient, as indicated by the low yields and high carbon residues.

Example I I I Carbon Residue. Wt. Percent 7 5 Yield, Vol. Percent Viscosity at 210 F. l, 100 650 OD Color 2, 00D 1,200 I 12. 5 13. 5

. 216 Extr. Col. Top Temp.. F 225 255 When compared with Example II, the contacting was more efiicient, as indicated by the somewhat higher yields at similar carbon residues.

Example IV Using a similar extraction tower and mixing device as that employed in Example III, a side stream of isobutane-oil mixture from the tower was mixed with fresh asphalt and a light fresh isobutane stream. The resultant mixture was injected into the middle of the column. The bulk of the fresh isobutane, amounting to about 85% of the total isobutane used, was injected directly into the bottom of the column. The over-all 6 fresh normal butane, amounting to about 85% of the total normal butane, was injected directly into the bottom of the column. The over-all isobutane feed ratio was about 14 to 1. A sumnormal butane feed ratio was about 14 to l. A mary of the pertinent data follows: 5 summary of the pertinent data follows:

Carbon Residue, Wr. Percent 7 5 Carbon Rcsiduawt. YPercent 12 9 Yield, Vol. Percent 32 23 Yield, Vol. Percent 56 42 Viscosity at 210 F 1, 100 65D Viscosity at 210 F i 3, 500 1,50() OD Color 2, D00 1,200 0D Color 1 7, 50D 2, 700 Gravity, A. P. I 12.5 13. 5 10 Gravity, A. P. I l0 11, 5 Slt. Pt oi Spent Asphalt M0 216 Slt. Ptof Spent Asphalt 280 250 Extr. Col. Top Temp., F 208 244 Extr. C01. Top Temp., c F 256 278 Example V In a similar extraction tower and mixing device as that used in Example III, asphalt was contacted with normal butane. The light normal butane-fresh asphalt feed stream was, before injection into the column, further mixed with the main normal butane feed, the entire mixture then being thoroughly agitated in a vessel equipped with a mechanical stirrer and fed into the column at the middle. The solvent feed ratio was about 14 to 1. A summary of the pertinent data follows:

Carbon Residue, Wt. Percent l2 9 Yield, Vol. Percent 52 38 Viscosity at 210 F 3,500 1, 500 OD Color 7, 50D 2,700 Gravi ,A. P. l() 11.5 Si t. Pt. of Spent Asphalt 272 248 Extr. Col. Top Temp., F 260 282 'I'hus higher yields of oil can be obtained by use of normal butane in place of isobutane, but by sacrificing quality.

Example VI In a similar extraction tower and mixing device as that used in Example III, a side stream of butane-oil mixture from the tower was mixed with fresh asphalt and a light fresh normal butane stream. 'I'he resultant mixture was injected into the middle of the column. The bulk of the 'I'he yields obtained in this contact are approximately 8% better than those of Example V for the same quality of oil. Again eicient contact was obtained with the oily butane, thereby permitting the bulk of the fresh normal butane to be introduced into the bottom for further countercurrent contact.

I claim:

In the production of oily compositions from asphaltic residua in which a mixture of butane solvent and asphalt in a solvent to asphalt ratio exceeding about 5:1 is mixed in an extraction zone at an elevated temperature below the critical temperature of the solvent and under superatmospheric pressure sufficient to maintain the solvent in the liquid phase, and in which an upper layer of butane solvent rich in extracted oil and a lower layer rich in asphalt are later formed, the improvement which comprises withdrawing a portion of said upper layer from the extraction zone, intimately mixing said portion of the upper layer with the asphaltic feed before the asphaltic feed contacts the raw solvent stream and before the asphaltic feed is charged to the extraction zone, withdrawing a portion of said lower layer from the extraction zone, intimately mixing said portion of the lower layer with the raw solvent stream before the raw solvent stream contacts the asphaltic feed and before the raw solvent stream is charged to the extraction zone.

RUDOLPH C. WOERNER.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,115,846 Frolich May 3, 1938 2,116,188 Churchill May 3, 1938 2,188,012 Pilat et al. Jan. 23, 1940 2,198,777 Laughlin Apr. 30, 1940 

